Cutting truck & bus emissions - The Vecto AirDrag Tool

Tesla Semi Explained: https://www.youtube.com/watch?v=Km1NHe0ZsVo Connect with me on Linkedin: https://www.linkedin.com/in/wouter-remmerie/ ---What is Vecto--- Within the quest to limit climate change, the pressure on heavy duty transport has been rising, and with good reason: trucks, buses and coaches together produce around a quarter of all CO2 emissions from road transport in the European Union. To ensure that the most fuel-efficient vehicle combinations are brought onto the market, the European Union developed the “Vehicle Energy Consumption calculation Tool”, or VECTO in short, a mandatory tool since January 2019 for new trucks & buses in a number of categories. Based on input parameters like rolling resistance, air drag, masses and inertias, gearbox friction, auxiliary power and engine performance, it simulates fuel consumption and CO2 emissions based on standardised driving cycles. So how do you obtain all these parameters? ---What is Vecto AirDrag--- Based on constant speed track tests and a massive set of measurement data, Vecto AirDrag allows you to calculate the air drag Cd*A, based based on force measurements: - Constant forces, that do not change with velocity (rolling resistance, bearing losses, and so on) - Air drag force, which scales with the square of the velocity To obtain the split between these forces, you can measure the force at 2 different velocities. If you then fit a curve through both low-speed and high-speed tests, including a constant and a quadratic term, you can isolate both components. ***The Track*** Tests are executed on a proving ground test track, with two straight parts running in opposite direction. Data is logged throughout the entire test, but it’s only the data captured on these straights that counts. ***Measurements*** - On the vehicle High-accuracy DGPS data Front axle rpm & torque (left and right) Wind speed & direction above the truck measured using an anemometer mounted on a pole Ambient temperature on the truck - At the fixed weather station on the proving ground Ground temperature and Air pressure & humidity are measured. ***Data evaluation*** Once all the tests have been performed and the data has been gathered, the constant speed tests are processed in 8 steps: 1: the instantaneous velocity readings are corrected using the average velocity over a test section. 2: the forces acting on the truck are calculated, based on the torque readings from the shafts and the engine or cardan speed. These are then corrected: - the force for climbing or descending is compensated for based on the road gradient & vehicle mass. - the correct air density is calculated using the temperature at the vehicle and pressure & humidity at the fixed weather station 3: validity criteria are applied to each constant speed test (speed & temperature ranges, ...) 4: CdA(beta) is calculated for each test by fitting a curve through the data. 5: result averaging per heading and then across headings. 6: extra checks (on rolling resistance, ...). 7: CdA(beta) conversion to CdA(0°) based on empirical data / vehicle type. 8: anemometer drag correction ---Optimizing for efficiency-- As you can imagine, running these tests requires large budgets & a lot of preparation effort, so you want to get it right the first time around. To know up front how changes in aerodynamics will impact vehicle efficiency, you can run aerodynamic simulations: 12--these allow you to calculate the CdA for each design concept and quantify the effects of replacing mirrors by camera’s, shielding the wheels, reducing the gap between tractor and trailer, and so on. You can then use the engineering mode of Vecto to assess the effect of these differences in aerodynamic coefficient on total vehicle efficiency. Once you’re comfortable enough with the predicted efficiency gains, you can move on to real physical testing, using the declaration mode of Vecto for the final analysis.

Supported by

  • Solar Impulse
  • iMec
  • Voxdale

Code contributions by

  • KU Leuven
  • Inholland
  • Linkoping University